A lonely scavenger burdened with a sack of refuse walks across the "Bordo Poniente" garbage dump in Mexico City, on January 18, 2012. Some six thousand tons of garbage from the second world most populated city were daily deposited here for about twenty five years until it was closed by the government last month. The dump has been considered as one of the main sources of greenhouse gases in Mexico. AFP PHOTO/ Yuri CORTEZ